Colloid transfer process



March 15, 1966 -r. l. ABBOTT COLLOID TRANSFER PROCESS Filed Jan. 16, 1963 FILM 0R PAPER SUPPORT l0 1! A EXPOSED AND TANNING DEVELOPED EMULSION LAYER UNTANNED l3 EMULSION A STRATUM 14 SILVER IMAGE m TANNED COLLOID RECEIVING SUPPORT FILM OR PAPER SUPPORT EXPOSED AND TANNING 17 DEVELOPED EMULSION LAYER UNTANNE D EMULSION STRATUM SILVER IMAGE IN TANNED OLL ID RECEIVING c o SUPPORT Thomaslbboli IN VENTOR.

AT'I' NEIYS United States Patent Office 3,240,600 Patented Mar. 15, 1966 3,240,600 CULLOID TRANSFER PROCESS Thomas I. Abbott, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Jan. 16, 1963, Ser. No. 251,875 12 Claims. (Cl. 96-28) This invention relates to photography and particularly to a colloid transfer process for obtaining copies of uniform density.

Various methods of forming an image in an unsensitized sheet by transfer from an originally sensitive layer have been described in the literature. In Yutzy and Yackel, US. Patent No. 2,596,756, there is described a procedure according to which a photographic image formed by tanning developing imagewise an unhardened gelatin layer and the unhardened areas are transferred to a dry absorbent receiving sheet by pressing the print after processing into contact with the dry absorbent surface, then stripping the two apart after a short interval of contact. In this process a stratum of the gelatin layer is adhered to the receiving surface and trans ferred, leaving behind the remainder of the gelatin layer containing part of the image. Upon rewetting the gelatin layer, successive transfers can be made. This method produces a positive transferred image if a positive is used to make the original exposure.

Normally, as multiple copies are made from an emulsion coated matrix, they decrease in image density from the first copy to the last copy until depletion of the matrix occurs. It has been desirable to find a means of reducing this density decrease whereby all of the copies have a more uniform image density until depletion occurs.

I have found a method of preparing a colloid transfer element which yields a more uniform distribution in the amount of silver transferred in making successive copies by coating at least one layer rich in silver halide under a colloid transfer emulsion of the type described in U.S. Patent 2,596,756.

One object of this invention is to provide a colloid transfer process in which the multiple copies have a more uniform density. Another object is to provide a photographic element comprising at least two unhardened emulsion layers which coact to produce transferred images having relatively uniform density. An additional object is to provide a variable ratio of gelatin-to-silver halide in coacting emulsion layers. Additional objects will be apparent from the following disclosure.

The objects of my invention are attained by coating two or more light-sensitive silver halide emulsion layers of the type disclosed in U.S. Patent 2,596,756 except that the emulsion nearest the support has a higher silverto-gelatin ratio than that normally used. Preferably 45 to 55% of the silver halide in the two layers is contained in the top layer, although 40 to 70% is a useful range. However, 60 to 90% of the total gelatin or similar colloid comprises the top layer, but our preferred range is from 70 to 80%. In the event that three layers are used, the ratio from the bottom layer to the middle layer and from the middle layer to the toplayer would be the same as the bottom layer to the top layer in the two layer system.

My invention will be better understood by reference to the accompanying drawings wherein FIG. 1 shows in enlarged cross-sectional view, the appearance of a processed photographic element carrying two) unhardened emulsion layers containing a silver image and showing the receiving support in the process of being removed from contact with the emulsion matrix and having transferred to the receiving support.

FIG. 2 shows a similar enlarged cross-sectional view to that of FIG. 1 except that three emulsion layers are shown comprising the matrix.

My invention will now be described in greater detail with reference to the accompanying drawings.

In the preferred embodiment of my invention, as shown in FIG. 1, I take a substantially unhardened light-sensitive gelatino silver halid emulsion 11 having a higher silver-to-gelatin ratio than normally used for coating on film, paper, or other support 10 and coated over this first coating a second unhardened light-sensitive, gelatino silver halide emulsion 12 having the normal silver-to-colloid ratio. The emulsion is reflex exposed, for example, with the emulsion surface in contact with the front of a sheet carrying printed matter. After this, the exposed layers are developed in the presence of a tanning developing agent which may have been incorporated in the emulsion layers of the type and the manner disclosed in U.S. Patent 2,596,756, in which case the development is by means of an alkaline solution comprising, for example, a 2% sodium hydroxide or sodium carbonate solution.

After exposure and development in the presence of a tanning developing agent, the processed emulsions are contacted against a receiving support 15 with the transfer of an undeveloped and untanned emulsion strata 14.

In FIG. 2 is shown a three layer system comprising a first gelatino silver halide emulsion 16, a second 17 and a third 18 having a ratio of silver halide to gelatin of the first layer 16 to the second 17 as the second to the third 18.

It will be appreciated that the receiving support may be any absorbent support such as paper, wood, cloth, etc.

The following examples are intended to illustrate our invention but not to limit it in any way.

Example 1 Layer I A. Silver chloride photographic emulsion weighing 3.2 kg. per mole of Ag and containing g. gelatin, g. 400.0 B. Developer dispersion, g. 115.8 C. Green sens. dye 1 mg./10 cc. methyl alcohol, cc. 8.8 D. Methylene Blue 3 mg./cc. H O, cc 12.5 E. 7 /2% Saponin aqueous solution, cc. 15.0

(A) is poured into (B) with rapid stirring and run through a colloid mill three times.

Layer II Same as Layer I except that this emulsion was coated over Layer I at a coverage of 176 mg. of A-g./ft. and 655 mg. gel./ft.

Processing Procedure:

Same as for the emulsion in US. Patent 2,596,756

(1) Reflex exposure (2) Activation by using an alkaline activator (3) Multiple transfers to a receiver In determining the difference in density, a visual difference is noticeable since the first copies obtained with the two-coat emulsion have a lower density than those obtained from a similar emulsion in which the total silver halide and total gel coated in the double coat system were instead coated in a single coat system. Subsequent copies in the single coat system, however, had a lower density than that in the double coat system. When the milligrams of silver per square foot distributed by the matrix in the single coated system were plotted against the number of copies, the values ranged from 44 down to mg. of silver per square foot for copies one through eight, whereas a uniform density of about was obtained for all eight copies for the two coat system.

Example 2 Layer I as in Example 1 coated at 137 mg. Ag/ft. 230 mg. gel/ft Layer II as in Example 1 coated at 141 mg. Ag/ftF, 516 mg. gel/ft. The particular copies obtained by the two coat system have a more uniform density within the range of 30 to mg. per square foot as compared to a single coat system wherein emulsion layer No. 2 was coated directly on the support at a coverage of 190 mg. of silver per square foot and 700 mg. gelatin per square foot, as previously described in US. Patent 2,596,756. Only 6 copies were obtainable and the decrease in density was indicated by the range of from for the first copy to 17 mg. of silver per square foot for copy six.

Example 3 A two coat system as described in Example 1 was prepared in which the first layer on the support contained 98 mg. silver halide and 160 mg. gelatin/fe The second coating contained 176 mg. silver and 655 mg. gel/ft. resulting in a ratio of the bottom layer to the top layer of 1.8 silver and 4.1 gelatin. The bottom layer contained 36% of the total silver, but only 19.6% of the total gelatin in the system. Uniform density copies were obtained.

Example 4 A two coat system similar to that described in Example 3 was prepared with 137 mg. silver halide/ft. in the bottom layer and 230 mg. gelatin/ft The top layer contained 141 mg. silver halide/ft. and 516 mg. gelatin/ft. resulting in a ratio the bottom layer to the top layer of 103 silver and 2.2 gelatin. The bottom layer contained 49% of the total silver and 32% of the total gelatin. Uniform density copies were obtained.

Where I refer hereinafter to a substantially unhardened gelatin emulsion layer I mean a layer that is not harder than would be the case with gelatin con taining 0.25 ounce of formaldehyde (40 percent, diluted 1 to 3 with water) per pound of gelatin when freshly coated, or 0.1 ounce of the formaldehyde solution per pound of gelatin for a sample aged 3 to 6 months.

In my system, a preferred range of coverage including two or more emulsion layers is about 100-500 mg. Ag/ft. as silver halide and 450-900 mg. gelatin/ft? However, a useful range may be 50-1000 mg. Ag/ft. silver halide and 300-1000 mg. gelatin/ft. Of course, these emulsions are prepared and coated under safelight conditions.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A photographic element for use in the colloid transfer process having thereon two optically-sensitized, lightsensitive, contiguous silver halide emulsion layers, said silver halide dispersed in an alkali-permeable, waterswellable unhardened colloid not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, having a first emulsion layer on the support and and a second emulsion layer coated over the first emulsion layer, the second emulsion layer containing 40-70% of the total silver halide in both emulsion layers and 60-90% of the total colloid present in both emulsion layers, said emulsion layers containing a total coverage of -500 milligrams silver per square foot as silver halide and a total coverage of 450-900 milligrams colloid per square foot.

2. A photographic element according to claim 1 in which the photographic emulsions contain a tanning developing agent.

3. A photographic element according to claim 1 in which the photographic emulsions contain a tanning developing agent and a non-tanning developing agent.

4. A photographic element for use in the colloid transfer process comprising a support having thereon two optically-sensitized, light-sensitive, contiguous unhardened gelatino-silver halide emulsion layers, said unhardened gelatin being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, having a first emulsion layer on the support and the second emulsion layer coated over the first emulsion layer, the second emulsion layer containing 40-70% of the total silver halide in both emulsion layers and 60-90% of the gelatin present in the total of the emulsion layers, said emulsion layers containing a total coverage of 100-500 milligrams silver per square foot as silver halide and a total coverage of 450-900 milligrams gelatin per square foot.

5. A photographic element according to claim 4 in which the photographic emulsions contain a tanning developing agent.

6. A photographic element according to claim 4 in which the photographic emulsions contain a tanning developing agent and a non-tanning developing agent.

7. A method of photographic reproduction comprising developing an exposed photographic element comprising a support having thereon two optically-sensitized, lightsensitive, contiguous silver halide emulsion layers dispersed in an alkali-permeable, water-swellable, unhardened colloid having a first emulsion layer on the support and a second emulsion layer coated over the first emulsion layer, said unhardened colloid being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, the second emulsion layer containing 40-70% of the total silver halide in both emulsion layers and 60-90% of the total colloid present in both emulsion layers, said emulsion layers containing a total af about 100-500 milligrams of silver per square foot as silver halide and 450-900 milligrams colloid per square foot, by developing with a silver halide tanning developer to form a hardened colloid image in the exposed areas of at least the second emulsion layer and leaving substantially unhardened colloid in the unexposed area of said layer, removing excess water from the surface of the said second emulsion layer, placing a sheet having an absorbent surface against said second emulsion layer while said emulsion layer is in condition to print and the surface of the second emulsion layer free of greasy material to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said second emulsion layer to transfer only a stratum of unhardened colloid of said layer to said sheet.

8. A method according to claim 7 in which the emulsion layers contain a tanning silver halide developer.

9. A method according to claim 7 in which the emulsion layers contain a tanning silver halide developing agent and a non-tanning silver halide developing agent.

10. A method of photographic reproduction comprising developing an exposed photographic element comprising a support having thereon two optically-sensitized,

light-sensitive, contiguous unhardened gelatino-silver halide emulsion layers being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, having a first emulsion layer on the support and a second emulsion layer coated over the first emulsion layer, the second emulsion layer containing 40-70% of the total silver halide in both emulsion layers and 60-90% of the total gelatin present in both emulsion layers, said emulsion layers containing a total of about 100500 milligrams of silver per square foot as silver halide and 450-900 milligrams gelatin per square foot, by developing with a silver halide tanning developer to form a hardened gelatin image in the exposed areas of at least the second emulsion layer and leaving substantially unhardened gelatin in the unexposed area of at least the second layer, removing excess Water from the surface of the said second emulsion layer, placing a sheet having an absorbent surface against said second emulsion layer while said second emulsion layer is in condition to print and the surface of the second emulsion layer free of greasy material to cause only said unhardened gelatin portion of said layer to adhere to said sheet, and

separating said sheet and said second emulsion layer to transfer only a stratum of unhardened gelatin of said layer to said sheet.

11. A method according to claim 10 in Which the emulsion layers contain a tanning silver halide developer.

12. A method according to claim 10 in which the emulsion layers contain a tanning silver halide developing agent and a non-tanning silver halide developing agent.

References Cited by the Examiner UNITED STATES PATENTS 2,596,756 5/1952 Yutzy et al 9628 2,685,510 8/1954 Yackel 96-68 2,716,059 8/1955 Yutzy et al 96-28 2,725,296 11/ 1955 Kendall 9659 2,725,298 11/1955 Yutzy et al 95--88 3,140,179 7/1964 Russell 96-68 20 NORMAN G. TORCHIN, Primary Examiner. 

1. A PHOTOGRAPHIC ELEMENT FOR USE IN THE COLLOID TRANSFER PROCESS HAVING THEREON TWO OPTICALLY-SENSITIZED, LIGHTSENSITIVE, CONTIGUOUS SILVER HALIDE EMULSION LAYERS, SAID SILVER HALIDE DISPERSED IN AN ALKALI-PERMEABLE, WATERSWELLABLE UNHARDENED COLLOID NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, HAVING A FIRST EMULSION LAYER ON THE SUPPORT AND AND A SECOND EMULSION LAYER COATED OVER THE FIRST EMULSION LAYER, THE SECOND EMULSION LAYER CONTAINING 40-70% OF THE TOTAL SILVER HALIDE IN BOTH EMULSION LAYERS AND 60-90% OF THE TOTAL COLLOID PRESENT IN BOTH EMULSION LAYERS, SAID EMULSION ALYERS CONTAINING A TOTAL COVERAGE OF 100-500 MILLIGRAMS SILVER PER SQUARE FOOT AS SILVER HALIDE AND A TOTAL COVERAGE OF 450-900 MILLIGRAMS COLLOID PER SQUARE FOOT.
 7. A METHOD OF PHOTOGRAPHIC REPRODUCTION COMPRISING DEVELOPING AN EXPOSED PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON TWO OPTICALLY-SENSITIZED, LIGHTSENSITIVE, CONTIGUOUS SILVER HALIDE EMULSION LAYERS DISPERSED IN AN ALKALI-PERMEABLE, WATER-SWELLABLE, UNHARDENED COLLOID HAVING A FIRST EMULSION LAYER ON THE SUPPORT AND A SECOND EMULSION LAYER COATED OVER THE FIRST EMULSION LAYER, SAID UNHARDENED COLLOID BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, THE SECOND EMULSION LAYER CONTAINING 40-70% OF THE TOTAL SILVER HALIDE IN BOTH EMULSION LAYERS AND 60-90% OF THE TOTAL COLLOID PRESENT IN BOTH EMULSION LAYERS, SAID EMULSION LAYERS CONTAINING A TOTAL OF ABOUT 100-500 MILLIGRAMS OF SILVER PER SQUARE FOOT AS SILVER HALIDE AND 450-900 MILLIGRAMS COLLOID PER SQUARE FOOT, BY DEVELOPING WITH A SILVER HALIDE TANNING DEVELOPER TO FORM A HARDENED COLLOID IMAGE IN THE EXPOSED AREAS OF AT LEAST THE SECOND EMULSION LAYER AND LEAVING SUBSTANTIALLY UNHARDENED COLLOID INTHE UNEXPOSED AREA OF SAID LAYER, REMOVING EXCESS WATER FROM THE SURFACE OF THE SAID SECOND EMULSION LAYER, PLACING A SHEET HAVING AN ABSORBENT SURFACE AGAINST SAID SECOND EMULSION LAYER WHILE SAID EMULSION LAYER IS IN CONDITION TO PRINT AND THE SURFACE OF THE SECOND EMULSION LAYER FREE OF GREASY MATERIAL TO CAUSE ONLY SAID UNHARDENED COLLOID PORTION OF SAID LAYER TO ADHERE TO SAID SHEET, AND SEPARATING SAID SHEET AND SAID SECOND EMULSION LAYER TO TRANSFER ONLY A STRATUM OF UNHARDENED COLLOID OF SAID LAYER TO SAID SHEET. 